Fossil fuels or petroleum-based fuels have formed the basis for energy production and transportation. In recent years, due to rising costs and threats of shortages and supply interruptions, biofuels have particularly received as alternative fuels to petroleum-based products.
Biofuel is generally regarded as any fuel derived from biomass. The term biomass is often used in regard to plant-based sources, such as corn, soy beans, flaxseed, sugar cane, and palm oil, but the term can generally extend to any recently living organisms, or their metabolic byproducts, that play a part in the carbon cycle.
The studies done into the production of bioenergy from biomass have mainly been into alternative fuels that can replace transportation oil-based fuel (gasoline and diesel). As an alternative to gasoline, bioethanol which is prepared by fermentation of sugar cane, corn or the like was developed and commercialized. Likewise, as an alternative to diesel, biodiesel, such as FAME, HBD or the like, which is prepared by treating plant-based oil such as palm oil, soybean oil or the like, was developed and commercialized.
However, in the prior art, there has been an ethical problem in that edible plants such as plants and plant oils are used as the raw materials to prepare bioethanol and biodiesel. In addition, supplying the raw materials is not easy, and the economy is being reduced rapidly due to a rapid increase in the cost of the raw materials. In an attempt to solve these problems, studies on the use of non-edible plants as raw materials have been actively conducted, but a clear solution has not yet been found.
Among recent studies on the preparation of transportation fuels from biomass is a study which has been receiving attention that is a method comprising obtaining C6 sugar/polyol from woody biomass through various pretreatment steps, preparing a mixture of alcohol, organic acid, cyclic furan and the like from the C6 sugar/polyol using a Pt—Re/C catalyst, and preparing oil fractions such as gasoline, aromatics and diesel from the mixture by various chemical reaction pathways [Science 322 (2008) 417]. However, due to low yield, high pretreatment cost, the use of a large amount of hydrogen, complicated reaction pathways, and the like, this method will require a long time until it is applied to actual commercial processes.
Volatile fatty acids (VFAs) can be obtained in high yield from various raw materials, including woody biomass, seaweeds and organic waste, by simple fermentation, and studies on the preparation of transportation oil from such volatile fatty acids are in progress. Generally, there is a known method for preparing mixed alcohols from the mixed fatty acids or mixed ketones obtained by fermentation. Furthermore, a method is known which comprises preparing mixed olefins by the dehydration of alcohols and oligomerizing the olefins to prepare gasoline and diesel fractions.
U.S. Pat. No. 5,874,263 discloses that volatile fatty acids or their metal salts can be prepared by anaerobic fermentation of biomass. Specifically, the productivity of volatile fatty acids and their calcium salts, which are obtained by fermentation, can be increased by pretreating biomass with slaked lime under anaerobic conditions and increasing the initial volatile fatty acid levels.
Methods of preparing volatile fatty acids or ketone mixtures using metal salts of volatile fatty acids produced by fermentation are as follows. U.S. Pat. No. 5,969,189 discloses methods of forming calcium carbonate by pyrolysis of calcium salts of volatile fatty acids prepared as described above, and preparing ketone mixtures from volatile fatty acids. U.S. Pat. No. 6,043,392 discloses a method comprising substituting metal salts of volatile fatty acids, prepared by anaerobic fermentation, with an amine to prepare amine carboxylates, and pyrolyzing the amine carboxylates, thereby preparing volatile fatty acids and preparing aldehyde, alcohol and lactic acid as byproducts.
Methods of preparing transportation fuels directly from the volatile fatty acids prepared by the above-described methods are as follows. U.S. Pat. No. 7,351,559 discloses a method of preparing ethanol usable as fuel by fermenting biomass to prepare acetic acid and acetate, which are then esterified to ethyl acetate, followed by hydrogenation. US 20080280338 discloses a method of preparing liquid fuel usable as transportation fuel by preparing acetylene from the alcohol and methane derived from volatile fatty acids, and converting the acetylene to ethylene, followed by oligomerization. US 20090239279 discloses a method for increasing the efficiency of preparation of liquid fuel by mixing a hydrocarbon and a pyrolysis oil obtained by biomass other than the above alcohol and methane and oligomerizing the mixture.
However, in the processes of obtaining branched fuels by oligomerization, there are shortcomings in that the catalyst is rapidly inactivated due to the production of coke, and thus a fluidized bed reactor having high equipment and operating costs should be used.
Furthermore, conventional biofuels such as bioethanol and biodiesel could substitute for only a portion of petroleum-based gasoline and diesel, because the physical properties thereof differ from those of these petroleum-based fuels. However, if transportation fuel or lubricating base oil prepared from biological sources has quality equal to or higher than that of conventional petroleum-based transportation fuel or lubricating base oil and can substitute for all of the conventional petroleum-based fuels, the technical value thereof appears to be higher.
In addition, there is a need for studies into methods capable of preparing branched non-polar paraffinic transportation fuel or lubricating base oil in high yield by carrying a catalytic reaction of volatile fatty acids from natural sources and subjecting the catalytic reaction products to aldol condensation, hydrogenation and hydrodeoxygenation alone or sequentially.